CISA: Erlang Erlang/OTP SSH Server Missing Authentication for Critical Function Vulnerability
CVSS 3.1
10.0critical
EPSS
99%p100
Published
()
KEV added
AI analysis
CVE-2025-32433 is a missing-authentication flaw (CWE-306) in the SSH server shipped with Erlang/OTP, the runtime and libraries of the Erlang programming language. An unauthenticated attacker can send specially crafted SSH protocol messages to a vulnerable Erlang/OTP SSH daemon before authentication and trigger remote code execution. Successful exploitation yields arbitrary command execution on the host with the privileges of the SSH service, and the CVSS scope change (S:C) indicates compromise can cascade to resources beyond the vulnerable component. Affected are any systems exposing the Erlang/OTP SSH server, including standalone Erlang deployments, Debian-packaged Erlang, and Cisco products that embed Erlang/OTP (e.g., Network Services Orchestrator, ConfD Basic, Ultra Packet Core). Exploitation is confirmed in the wild: a public proof-of-concept exists, the bug was added to CISA KEV on 2025-06-09, and researchers report a surge in exploitation attempts, with roughly 70% of observed attacks targeting OT firewalls.
What to do: Upgrade Erlang/OTP to OTP-27.3.3, OTP-26.2.5.11, or OTP-25.3.2.20 depending on the release branch, and apply the corresponding updates from Cisco and Debian for embedded/packaged Erlang. Until patched, disable the Erlang SSH daemon or restrict access to it with firewall rules, prioritizing internet-exposed hosts and OT firewall devices where ~70% of observed attacks have landed. Federal agencies must apply mitigations per vendor instructions under the KEV/BOD 22-01 requirements.
Affected
Erlang/OTP (SSH server)
all versions prior to OTP-27.3.3 (27.x), prior to OTP-26.2.5.11 (26.x), and prior to OTP-25.3.2.20 (25.x); fixed in those versions
largetens of thousands of internet-exposed Erlang/OTP SSH servers, plus an unknown additional embedded installed base in telecom/network equipment (Cisco NSO,… — Public internet scans reported around disclosure showed on the order of tens of thousands of exposed Erlang SSH daemons, and Erlang/OTP is widely embedded in telecom and OT infrastructure, though exact embedded deployment counts are not in…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
Erlang/OTP is a set of libraries for the Erlang programming language. Prior to versions OTP-27.3.3, OTP-26.2.5.11, and OTP-25.3.2.20, a SSH server may allow an attacker to perform unauthenticated remote code execution (RCE). By exploiting a flaw in SSH protocol message handling, a malicious actor could gain unauthorized access to affected systems and execute arbitrary commands without valid credentials. This issue is patched in versions OTP-27.3.3, OTP-26.2.5.11, and OTP-25.3.2.20. A temporary workaround involves disabling the SSH server or to prevent access via firewall rules.
CISA Known Exploited Vulnerability
Affected
Erlang Erlang/OTP
Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Attackers actively exploit CVE-2025-32433, a CVSS 10.0 unauthenticated RCE in Erlang/OTP SSH, heavily targeting OT and critical infrastructure networks.
CVE-2025-32433 enables unauthenticated RCE in Erlang/OTP's SSH daemon via SSH connection protocol messages (codes >= 80) processed before authentication, affecting versions before OTP-27.3.3, OTP-26.2.5.11 and OTP-25.3.2.20. Unit 42 recorded a spike in exploitation between May 1-9, 2025, with 70% of detections on firewalls protecting OT networks, disproportionately affecting healthcare, agriculture, media and high technology. Observed payloads bind TCP-connected shells or launch Bash reverse shells to hosts like 146.103.40.203:6667, with randomized DNS lookups under dns.outbound.watchtowr.com indicating OAST-driven blind RCE validation.